Qualitative reasoning for admission control in ATM networks

Abstract

Asynchronous Transfer Mode (ATM) provides transport functionality to the future Broadband Integrated Service Digital Network, ATM networks are connection oriented and Connection Admission Control (CAC) is a preventive control procedure responsible for determining whether a connection request is admitted or denied. There is a trade-off between the accuracy and the evaluation time on the CAC schemes. Most accurate methods spend excessive time on evaluations and consequently the request is rejected due to time-out. A possible approach is to evaluate some possible future situations (pre-evaluation). These results would be previously evaluated and saved on a table. Between consecutive connection requests, the evaluation system evaluates in advance the future response for each class of traffic.

The drawback occurs when two, or more, connection requests arrive close in time, so that the on-line pre-evaluation scheme has ‘Unknown’ on the response vector. The objective of this work is to cover the possible lack of information by using Qualitative Reasoning (QR). QR enables calculations with non-numerical descriptions and still producing coherent results.

This work has been supported by CICYT (Spanish Education Ministry) under contract TIC95-0982-C02-